Indinavir has been shown in laboratory tests to have a strong effect on slowing the growth and spread of HIV-1. HIV-1 infection is thought to be the main cause of the acquired immunodeficiency syndrome (AIDS), which results in a gradual wearing down of the body's defenses against a variety of germs and other diseases. The main purpose of this study is to determine the safety and activity of indivavir in combination with ritonavir in HIV-infected patients who have failed protease inhibitor therapy.